Solids drying process



y 1970 K. c. HELLWIG I 13 SOLIDS DRYING PROCF'JL'I Filed Feb. 21, 1968GAS: WATER VAPOR nor on SCRU'BBER 2o GAS:

WATER VAPOR,

FINES.

' 10 GRINDNG & HOT on ,FINES name / 24 swam moron &

PULVERIZED COAL an L 26 I PRODUCTS HOT GAS y KATHERINE C. HELLWIGlNvm'm/c.

' AGENT United States Patent 3,519,552 SOLIDS DRYING PROCESS KatherineC. Hellwig, Trenton, N.J., assignor to Hydrocarbon Research, Inc., NewYork, N.Y., a corporation of New Jersey Filed Feb. 21, 1968, Ser. No.707,061 Int. Cl. C10g 1/00 U.S. Cl. 2088 Claims ABSTRACT OF THEDISCLOSURE A process for drying a particulate carbonaceous solidmaterial by passing a hot, relatively moisture-free gas through thematerial and scrubbing the gas with a liquid which is at a highertemperature than the gas, whereby the liquid retains the fines and themoisture from the solids material is carried away in the gas.

BACKGROUND OF THE INVENTION This invention pertains to the drying ofsolid particulate material and subsequent removing of the finescontained therein from the drying gas. More particularly, it pertains tothe drying of a solid carbonaceous material, such as bituminous andsubbituminous coals, lignite and peat, which has been pulverized priorto its introduction to a hydrogenation and/ or hydrocracking process forthe purpose of converting said material to liquid hydrocarbons.

In such systems, it is necessary that the water be removed from thematerial prior to processing in order to prevent foaming and lowering ofhydrogen partial pressures within the reaction zone. The moisturecontent of the material is reduced by grinding or pulverization alongwith either concurrent or subsequent drying. The most eflicient way todry such materials is to pass a hot gas which is inert to the material,such as a hot flue or vent gas, through the pulverizing equipment so asto dry the material concurrently with the pulverizing operation.However, it is not necessary that such drying procedure take placeconcurrently with the pulverizing operation as the particulate materialmay be separately dried in a fluidized bed type system.

A major disadvantage of the above procedure, however, is the excessivecarryover of fine particles with the drying gas. It is necessary thatthese particles be recovered in order to make the process commerciallyfeasible, since the loss of the fines is extremely expensive. Inaddition, the problems of air pollution which have recently come to thefore now require that such fines not be discharged into the atmosphere.Today, in most areas, there is statutory prohibition of such discharge.A number of methods for removal of such particles has been developed,but have been shown to be quite expensive. An example in the use of bagfilters or other dry recovery methods for separating the line particlesfrom the gas.

SUMMARY OF THE INVENTION I have invented a method which provides forremoval of moisture from a particulate solid material and subsequentrecovery of the fines contained in the removal gas, while allowing themoisture contained in the drying gas to be carried away. Moreparticularly, with respect to a coal hydrogenation process, my inventioninvolves the removal of the fines-containing drying gas from theparticulate coal and passing the hot gas through a hydrocarbon liquidwhich is at a temperature higher than that of the gas. The fines areretained in the liquid, however, the moisture passes through the liquidand out with the gas. Numerous mechanical scrubbing methods forcontacting the liquid and gas are well known in the art.

With respect to a coal hydrogenation process, the dried pulverized coalis usually slurried in a hydrocarbon slurry oil, obtained eitherindependently or from the hydrogenation process itself, and the slurryis then introduced into a catalytic hydrogenation zone. By use of myinvention, it is possible to directly introduce the fines-containinghydrocarbon liquid into the reaction zone, so that an intermediateseparation step of the fines from the carrying material is unnecessary.A further modification of my invention is the use of the slurry oil inthe hydrogenation process as the scrubbing liquid for thefinescontaining gas. In this manner, the hot gas, after having beenpassed through the solids material, is passed in contact with the slurryoil. The coal fines are then retained in the oil and passed into thecoal hydrogenation zone, while the moisture contained in the drying gasis retained in said gas and passes out of the scrubbing zone in the formof a vapor. Since the liquid is at a higher temperature than the gas,the moisture will not be retained in the hydrocarbon liquid.

DESCRIPTION OF THE DRAWING The drawing is a schematic flow diagram of aparticulate solids drying process.

DESCRIPTION OF THE PREFERRED EMBODIMENT While my invention is applicableto any particulate solids drying process where it is required to removethe water vapor from the solids, and to recover the fines, it isparticularly useful in coal hydrogenation processes wherein the liquidused to remove the fines from the drying gas can be introduced directlyto the coal hydrogenation reactor. Specifically, in processes of thetype disclosed in the Johanson U.S. Pat., Re.: 25,770 and the Schuman etal. U.S. Pat. 3,321,393, my invention is especially useful, since inthose processes, a hot oil is removed from the reactor eflluent and isused to slurry the pulverized coal for introduction into the reactor.Such processes use the so-called ebullated bed type of contactingsystems, wherein the coal in an oil slurry, is passed upwardly withhydrogen through a catalytic contact zone at high temperatures andpressures. The solid coal passes through the expanded catalytic bed andis converted to liquid hydrocarbons therein. Gaseous and liquideflluents are removed from the reaction zone along with ash andunconverted coal. A selected portion of the effluent is recycled to aslurry tank where a slurry mixture of the hot oil and pulverized coal ismade, said slurry being then passed into the reaction zone. A particularembodiment of my invention with reference to the coal conversion processdescribed above, is shown in the drawing and is outlined as follows:

Particulate coal, at a nominal size of about 1%" diameter at 10 isintroduced to the drying and grinding zone 14 along with a hot gas at12. The only requirements for this gas is that it be inert tocarbonaceous materials under the grinding and drying conditions and alsothat it be relatively moisture free. Gases, such as nitrogen, carbondioxide, carbon monoxide and combinations thereof in addition to fluegases obtained from the combustion of fuel, etc., may be used. It wouldusually be more economical if gas which is readily available at thesite, such as a vent gas from the hydrogenation process, is used as thedrying gas. The temperature of the gas at the drying process inlet issubstantially higher than that of the outlet, it being usual tointroduce gas at about 500-700 F. and remove it at about -300 F. Thecontacting system used within the drying zone 14 may be of the fluidizedbed type or other systems well known to the art.

After the contacting in zone 14, the hot gas which contains water vaporand fines is removed through line 16 to scrubber 18. Here the gas iscontacted with a hot hydrocarbon oil from line 20. The temperatures ofthe hydrocarbon liquid must necessarily be above that of the finescontaining gas. It is normal in these processes for the oil to be attemperatures above 300 F. The scrubbed gas containing only the watervapor is removed overhead at line 22 while the hot oil containing thecoal fines is removed through line 24.

The dry pulverized coal removed from the grinding zone 14 through line26 and the hot oil containing the fines in line 24 are introduced to aslurry tank 29. The slurry is then introduced through line 28 to thecoal hydrogenation reactor 30.

As has been discussed above, the reactor system in zone 30 may be any ofthe numerous catalytic contacting systems known to the art such as theebullated bed, slurry systems, etc. The gaseous and liquid products fromthe coal conversion step are removed through line 32, hot vent gases areremoved in line 12 and may be used as the drying gas by recycling backto the grinding and drying zone 14. Alternatively, an independent inertgas source may be used. A hot hydrocarbon oil is removed from thereactor effluent in line and is returned to the scrubber 18 for use asthe scrubbing oil. Alternatively, an independent oil source external ofthe system may be used as the scrubber. The only requirements of saidoil is that it be compatible with introduction to a coal hydrogenationreactor if recycle is desired and, also, that its temperature be higherthan that of the gas containing the water vapor and fines. A temperaturedifferential between the drying gas and the scrubbing liquid of at leastabout 20 F. is needed in order to assure minimum transfer of moisturefrom the gas to the oil.

In a process as described above for the treatment of 43 tons of coal perhour, the preferred conditions are as follows:

Feed:

Type-coal Size (after grinding)minus 40 US. mesh Moisture:

Initial12 wt. percent Final2 wt. percent Drying gas:

Type-flue gas Drying gas temperature: Inlet-650 F. Outlet-l70 F. Gasrate-43,000 ftfi/ min. measured at 170 F. (30

ft. lb. coal feed) Scrubber conditions:

Oil temperature-300 F. Oil rate-230 bbl./ hour Obviously, manymodifications and variations of the invention as hereinabove set forthmay be made without departing from the spirit and scope thereof and,therefore, only such limitations should be imposed as are indicated inthe appended claims.

What is claimed is:

. 1. In a process for the hydroconversion of solid carbonaceousmaterials selected from the group consisting of coal, lignite, peat andmixtures thereof wherein ground,

dry carbonaceous solids are fed in a slurry to a reaction zone forconversion in the presence of hydrogen to hydrogenated products whereinthe improvement comprises:

.(a) drying the ground solid carbonaceous material in a drying zone indirect contact with a heated inert gas selected from the groupconsisting of nitrogen, carbon dioxide, carbon monoxide, flue gas andmixtures thereof;

(b) removing from said step (a) a gaseous effluent comprising inert gas,moisture and entrained solid carbonaceous material;

(c) scrubbing said gaseous efiluent with a liquid bydrocarbon oil havinga temperature of at least 300 F. and higher than the temperature of saidgaseous efiluent to remove said entrained solid carbonaceous materialthereby forming a slurry;

(d) removing from step (c) an entrained solid carbonaceousmaterial-free, moisture containing vent (e) passing said slurry to saidreaction zone for by droconversion.

2. The process of claim 1 wherein the temperature of the inert gasenters the drying zone between about 500 and about 700 F. while thetemperature of the inert gas leaving the drying zone is between aboutand about 300 F.

3. The process of claim 1 wherein, in the scrubbing step, a portion ofthe liquid hydrogenated products boiling above about 300 F., and formedin the hydroconversion of said solid carbonaceous materials, are used asthe liquid hydrocarbon oil to form said slurry.

4. The process as claimed in claim 2 wherein the carbonaceous materialis coal having a moisture content of about 12 weight percent, the coalbeing ground to about minus 40 U .S. mesh and wherein the inert gas isfiue gas, the temperature of which prior to the contacting step is about650 F. and after the contacting step is about F., the rate of the gasthrough the contacting step being about 30 cubic feet per pound of coalfeed, said rate being measured at 170 F. whereby the moisture content ofthe coal is reduced to about 2 weight percent and wherein the gas, afterthe contacting step, is scrubbed with slurry oil having a temperature ofabout 300 F. the oil feed rate to the scrubbing step being about 5.35barrels per ton of coal feed.

5. The process as claimed in claim 3 wherein, in the scrubbing step, thevent gas temperature is less than about 300 F. and the slurry oiltemperature is greater than about 300 F. and wherein the temperaturedifferen tial between the gas and the oil is at least about 20 F.

References Cited UNITED STATES PATENTS 2841,534 7/1958 Skaperdas 20882,741,549 4/1956 Russell 208--8 3,321,393 5/1967 Schuman 208-10 Re.25,770 4/ 1965 Johanson 2081 0 2,738,311 3/1956' Frese 20 8-8 DELBERT E.GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner

